A primary difficulty in treating diseases of the eye is introducing drugs or therapeutic agents into the eye and maintaining these drugs or agents at a therapeutically effective concentration in the eye for the necessary duration. Systemic administration may not be an ideal solution because, often, unacceptably high levels of systemic dosing are needed to achieve effective intraocular concentrations, with the increased incidence of unacceptable side effects of the drugs. Simple ocular instillation or application is not an acceptable alternative in many cases, because the drug may be quickly washed out by tear-action or pass from the eye into the general circulation. Suprachoroidal injections of drug solutions have also been performed, but again the drug availability is short-lived. Such methods make it difficult to maintain therapeutic levels of drug for adequate time periods.
Efforts to address this problem have lead to the development of drug delivery devices, or implants, which can be implanted into the eye such that a controlled amount of desired drug can be released constantly over a period of several days, or weeks, or even months. Many such devices have been previously reported.
Various sites exist in the eye for implantation of a drug delivery device or implant, such as the vitreous of the eye, anterior or posterior chambers of the eye, or other areas of the eye including intraretinal, subretinal, intrachoroidal, suprachoroidal, intrascleral, episcieral, subconjunctival, intracorneal or epicorneal spaces. Wherever the desired location of implantation, typical methods of implantation all require relatively invasive surgical procedures, pose a risk of excessive trauma to the eye, and require excessive handling of the implant. For example, in a typical method for placement in the vitreous, an incision is made through the sclera, and the implant is inserted into and deposited at the desired location in the vitreous, using forceps or other like manual grasping device. Once deposited, the forceps (or grasping device) is removed, and the incision is sutured closed. Alternatively, an incision can be made through the sclera, a trocar can be advanced through the incision and then the implant can be delivered through the trocar. Similar methods can be employed to deliver implants to other locations, e.g., implantation in the anterior chamber of the eye through an incision in the cornea.
The drawbacks of such techniques for implant delivery are many. Extensive handling of the implant is necessitated in these techniques, creating a risk that the implant will be damaged or contaminated in the process. Many such implants are polymer-based and relatively fragile. If portions of such implants are damaged and broken off, the release profile and/or effective therapeutic dose delivered by the implant once placed will be significantly altered. In addition, achieving reproducible placement from patient to patient can be difficult using these methods. Also of import is that fact that such techniques may require an opening in the sclera large enough to require suturing. Thus, such techniques are typically performed in a surgical setting.
A more facile, convenient, less invasive, and/or less traumatic means for delivering implants into the eye would be desirable.